Anyone ever noticed how bright lights IRL, at least on camera, become white? In Cycles a crazy strong red light stays red. So I made some adjustable nodes to add that. Sorry if it’s been done before, tried searching if anyone has done this with no relevant results.
There’s another solution you can try, don’t use a lamp color with a saturation value that’s either at or close to 1 (which appears to be the case here).
That’s probably because it’s not a pure red light IRL. If something like an intense red laser was shone on your object, then you might see something like the top picture.